hurricane sandy. the largest atlaá> there's two things to think about. one is, will there be more storms? and the second is, will more of those storms be intense? >> reporter: john mutter teaches environmental science at colombia university. >> what's happening is that if the world is warmer overall, the area that's occupied by the tropics will get larger. so if the tropics expand, they'll bring with them their tropical weather which includes hurricanes. so imagine that now we had ten hurricanes per year and two of them are really monsters. in the future, the expectation is there will still be ten but four of them will be monsters. >> reporter: there may be plenty of legitimate scientific disagreements and plenty of nasty bickering online about how much climate change we're seeing now. but the really frightening part is what's coming. >> i can actually show you temperature over centuries.